Ozone present in the upper atmosphere acts as a natural barrier which protects the environment from excessive solar ultraviolet radiation. It is believed that industrial and private usage of chlorofluorocarbons significantly depletes the concentration of ozone in this protective stratospheric barrier. Chlorofluorocarbons migrate into the stratosphere whereupon they are exposed to ultraviolet light which causes the chlorofluorocarbon molecules to dissociate. The resulting chlorine atoms catalyze a conversion of ozone to oxygen. It is believed that a single chlorine atom can destroy approximately 100,000 ozone molecules and that this ozone loss permits an increase in the amount of ultraviolet light reaching the earth's surface. Excessive ultraviolet irradiation is believed to contribute to serious health and environmental problems. Some health problems linked to ozone depletion include skin cancer, immune deficiencies and cataracts. Environmental problems that may result from diminished ozone are damage to crops and plankton which are critical to the functioning of the marine ecosystem.
The detrimental atmospheric chlorofluorocarbons are produced by halocarbon aerosol propellants, refrigerants and foams. It is believed that the chlorofluorocarbons of particular concern are CCl.sub.2 F.sub.2 and CCl.sub.3 F which have been released in large quantities over time and have the stability to reach the upper atmospheric layers. Although the manufacture of aerosol products containing these chlorofluorocarbons has been banned in the United States and other countries since Dec. 15, 1978, chlorofluorocarbon aerosols are not banned in all countries. Furthermore, chlorofluorocarbons are used as refrigerants in air-conditioning, blowing agents for forming polyurethane foams, dry-cleaning solvents and degreasing agents in the aerospace, electronics and specialty clothing industries (i.e., fur and leather). Additional uses for chlorofluorocarbons have been found in the synthesis of commercially important fluorovinyl monomers.
Photocatalyzed reactions using titanium dioxide to remove halocarbons from waste hydrocarbon liquids or vapors and drinking water have been described in D. F. Ollis, C-Y. Hsiao, C-L. Lee, Heterogeneous Photocatalysis: Degradation of Dilute Solutions of Dichloromethane (CH.sub.2 Cl.sub.2), Chloroform (CHCL.sub.3) and Carbon Tetrachloride (CCl.sub.4) with Illuminated TiO.sub.2 Photocatalyst, J. Catal., Vol. 82, p.p. 418-423 (1983) which is incorporated herein by reference.